The present invention relates to an accumulator for evaporating and condensing a refrigerant in a pressure vessel thereof to control pressure or the amount of refrigerant in a closed loop type controlled unit.
As compared to use conditions on the ground, electronic devices equipped for a spacecraft, such as a space station or a space satellite, are used under more severe thermal environment. For this reason, such spacecraft electronic devices are typically cooled by a radiator system to keep their temperature in the allowable range. Heretofore, various techniques including a heat pipe have been used as the radiator system. For example, the radiator system suitable for a large-scaled spacecraft includes a two-phase flow loop radiator system based on evaporation and condensation of refrigerant.
As shown in FIG. 8, this two-phase flow loop radiator system comprises: a closed loop type controlled unit 7 including an evaporator 1 disposed in a spacecraft, a condenser 2 disposed on the side of outer space, a piping 3 for providing fluid communication between them, a pump 4 and valves 5, 6 interposed in the piping 3. Further, an accumulator 8 is connected with the downstream side of the evaporator 1.
FIG. 9 shows a conventional example of the accumulator 8 which is provided with a liquid-phase refrigerant holding member 10 in a pressure vessel 9 thereof. The liquid-phase refrigerant holding member 10 comprises a plurality of flat-plate-shaped vanes 12 (eight vanes in FIG. 9) each extending radially about a center shaft 11, and a wick 13 provided along the inner wall of the pressure vessel 9 to surround the vanes 12. Further, a heater 14 and a cooler 15 are provided on the outer peripheral wall of the pressure vessel 9 to surround the outer peripheral wall at their vertically separated positions. Further, a connection port 16 is provided at the central portion of the lower end of the pressure vessel 9. The connection port 16 is in fluid communication with the controlled unit 7.
For activating the two-phase flow loop radiator system, in advance, the controlled unit 7 is filled with a refrigerant, and the liquid-phase refrigerant excessively supplied to the controlled unit 7 is collected and stored in the accumulator 8. In this state, upon activating the two-phase flow loop radiator system, the liquid-phase refrigerant in the evaporator 1 absorbs heat generated by electronic devices. Thus, the refrigerant is evaporated and vaporized, and is then transferred to the condenser 2 through the piping 3. The heat of the vapor-phase refrigerant transferred to the condenser 2 is released to outer space through the condenser 2. Thus, the refrigerant is condensed and liquefied again, and is then returned to the evaporator 1 through the piping 3, valve 6 and pump 4. Subsequently, the same cycle is repeated during the operation of the two-phase flow loop radiator system. During these cycles, the heater 14 or the cooler 15 of the accumulator is controlled in response to variance in heat load from the electronic devices of the spacecraft to evaporate or condense the refrigerant in the pressure vessel 9. For example, when the vanes 12 and the wick 13 are heated by the heater 14, the liquid-phase refrigerant held therein is evaporated. Thus, the pressure in the pressure vessel 9 is increased, and thereby the pressure in the controlled unit 7 is increased. When the vapor-phase refrigerant in the pressure vessel 9 is cooled by the cooler 15, the vapor-phase refrigerant is condensed, and the condensed refrigerant is absorbed by the vanes 12 or the wick 13. Then, the liquid-phase refrigerant flows into the controlled unit 7 through the connection port 16. In this manner, the pressure and the refrigerant amount in the controlled unit 7 is varied by changing the pressure and the liquid-phase refrigerant amount in the accumulator 8, and thereby the cooling capacity of the two-phase flow loop radiator system is controlled to keep the temperature of the electronic devices in the allowable range.
However, in the above conventional accumulator 8, when the pressure vessel 9 is heated under microgravity condition, the vapor-liquid interface of the refrigerant becomes unstable as shown in FIG. 10. Thus, the mixture of vapor-phase and liquid-phase refrigerants can flow from the connection port 16 into the controlled unit 7, resulting in deteriorated controllability of the controlled unit 7.
Further, since the vanes 12 are formed in flat plates, each refrigerant holding capacity of the vanes 12 is low. Thus, in order to hold a desirable amount of refrigerant, it has been required for the vanes 12 to have enlarged holding area or large number of vanes. As a result, the pressure vessel 9 has been undesirably enlarged, and thereby the accumulator 8 has suffered from the difficulty in downsizing and weight reduction.
Further, the liquid-phase refrigerant held by the vanes 12 tends to be concentrated in a narrow region due to surface tension thereof. Thus, most of the liquid-phase refrigerant undesirably is concentrated around the center shaft 11 remote from the cooler 15, resulting in deteriorated thermal controllability during heating or cooling.
In order to solve the above problems, it is therefore an object of the present invention to provide an improved accumulator capable of achieving desired downsizing and weight reduction with excellent controllability.
According to the present invention, there is provided an accumulator for evaporating and condensing a refrigerant in a pressure vessel thereof to control pressure or the like in a closed-loop type controlled unit, comprises a liquid-phase refrigerant holding element for holding the refrigerant in liquid phase, a heater for heating and evaporating the refrigerant in liquid-phase, a cooler for cooling and condensing the refrigerant in vapor-phase, and a connection port in fluid communication with the controlled unit. The liquid-phase refrigerant holding element includes a vane made of a material capable of absorbing the refrigerant in liquid phase, and the end of the vane has a shape in contact with the inner surface of the pressure vessel.
Preferably, the vane is formed in a wave shape.
The connection port may be disposed between the inner surface of the pressure vessel and the end of the vane.
Further, the connection port may include a slit facing to a space between the inner surface of the pressure vessel and the end of the vane to allow the refrigerant in liquid phase to flow in and out through the slit.
The liquid-phase refrigerant holding element may include a wick provided on the inner surface of the pressure vessel. In this case, the wick is made of a material capable of absorbing the refrigerant in liquid phase.
The wave-shaped vane may be provided in a plural number. In this case, the connection port is provided in the space between each of the plurality of vanes and the inner surface of the pressure vessel.
Further, the plurality of wave-shaped vanes may include a crossing portion therebetween. The crossing portion has a surface smoothly connected to each of the vanes.
In the above structure, when the pressure vessel is cooled by the cooler, the vapor-phase refrigerant in the pressure vessel is condensed and liquefied. The resulting liquid-phase refrigerant is absorbed by the wick or the vane, and then flows into the controlled unit through the space, the slit and connection port. Thus, the refrigerant amount in the controlled unit is increased.
When the pressure vessel is heated by the heater, the liquid-phase refrigerant held by the vane (and the wick) is evaporated and vaporized. Thus, the pressure in the pressure vessel is increased, and thereby the pressure in the controlled unit is increased.